<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        // let num = 20;
        // let uname = '张三';
        // console.log(num);
        // console.log(uname);

        let age = prompt('请输入你的年龄');
        document.write('你的年龄是' + age + '岁');
    </script>
</body>

</html>